The present invention relates to a blast furnace and a method for operating a blast furnace which may be employed for increasing the capacity or the throughput.
Metallurgical plants are plants for processing metal ore, wherein the central element of such a metallurgical plant is a blast furnace. These metallurgical plants have been known for a long time. A blast furnace is fed with raw materials which comprise metal ore, additives and heating material. Usually coal or coke is used as a heating material, wherein coal and coke produce heat by burning in the presence of air on the one hand and wherein coal and coke also function as reduction agents for the metal ore since the metal ore is basically comprised of metal oxide. When reducing metal ore in a blast furnace, various gases are produced, these being collectively known as furnace gas or flue gas. Said furnace gas usually contains a substantial amount of carbon dioxide (CO2). Carbon dioxide is a greenhouse gas and in recent years more and more effort has been made to prevent greenhouse gases or to convert them, as these greenhouse gases are regarded as being detrimental to the climate.
In the field of metal production, it is a general aim to use as few raw materials and heating materials as possible, as these materials are expensive and it is expensive to transport them. Much effort has been made to reduce the amount of coke/coal used in the production process. One approach was blowing coal dust into the blast furnace, and another approach was producing carbon monoxide as a reduction gas, either in the blast furnace itself or in a separate gasification reactor outside the blast furnace. From EP 09318401 A1, it is known to blow a portion of the carbon required for reducing the metal ore into the blast furnace in the form of a substitute reduction material. In this sense, e.g. natural gas, heavy oil, fine coal and similar materials having a high carbon content may be used as a substitute reduction material. These materials may be directly blown into the blast furnace shaft or may be gasified outside of the blast furnace shaft in a separate gasification reactor so as to form a reduction gas. Subsequently, such a reaction gas may be directed into the blast furnace shaft. The method known from EP 09318401 A1 may provide a possibility to reduce the amount of coal or coke consumed and enable materials that are difficult to process to be made use of as a substitute reduction material, but the problem of high CO2 emission in the metal production process has not been solved.
From the post-published German patent application No. 10 2013 009 993, there is known a blast furnace and a method for processing metal ore which are suitable for reducing CO2 emissions at high throughputs and reducing the quantity of additives and heating materials compared with metallurgical plants used in former times. Furthermore, DE 10 2004 036 767 B4 discloses a method for producing pig iron in a blast furnace which is operated with CO2-free furnace gas that is fed-back to the furnace with added oxygen and hydrocarbons. DE 1 928 981 A1, describes a method for producing pig iron in a blast furnace wherein the furnace gas is freed of dust whereafter hydrocarbons are added. The furnace gas is then heated and fed back into the blast furnace. From WO 2012/085 449 A1, there is known a method for producing pig iron in a blast furnace wherein CO2 is removed from the furnace gas which is then fed back into the blast furnace shaft.
The present invention is directed toward a blast furnace and a method for operating a blast furnace which are suitable for reducing CO2 emissions at high throughputs and wherein the quantity of additives and heating materials are reduced compared with metallurgical plants used at present. Furthermore, the capacity of the blast furnace is to be increased.